3.2 - Specialisation of Plant Cells

Autotroph

Makes organic materials from inorganic sources - make their own food using light, water or CO2
e.g. plants

Heterotroph

Need organic material to make food - depend on other sources for their food
e.g. animals

Chemotrophs

Takes inorganic chemicals and turns it into food
e.g. bacteria

What two systems can vascular plants be divided into?

Shoot and root systems

What are the four types of tissue within plans?

Dermal:

• Outside tissue (epidermis)

• Used for protection and water loss

Vascular:

• Vein systems (transport system)

Ground:

• Collenchyma

• Parenchyma

• Sclerenchyma

Meristematic:

• Growth tissues

• Found in roots and stem

What are the differences between xylem and phloem?

Xylem:

• Dead cells

• Thick cell walls (not lose water)

• Cell wall material: lignin

• Impermeable (cell wall too thick)

• No cytoplasm (dead cells)

• Transports water and minerals

• Carried to leaves

• Flows upwards

Phloem:

• Living cells

• Thin cell walls (moves out food at different points)

• Cell wall material: Cellulose

• Permeable

• Cytoplasm lining

• Transports food

• Carried to growing parts (cell division locations) and storage organs

• Flows up and down

What are the differences between monocot and dicot plant arrangements?

Monocot:

• Root: Xylem and phloem in a ring

• Stem: Vascular bundles scattered

• Leaf: Leaf veins form a parallel pattern

• Flower: Flower separates in multiples of threes

Dicot (eudicot):

• Root: Phloem between arms of xylem

• Stem: Vascular bundles in a ring

• Leaf: Veins form a net pattern

• Flower: Flower separates in multiples of fours and fives

What are the different ways that water can move through the xylem?

Transpiration:

• Evaporation of water from leaves through the stomata (stoma) pores

• Stoma can be opened and closed depending on various conditions (opens when full of water and closed when levels are low)

• As water leaves, this causes a negative pressure, pulling the water up from the roots and soil (why it only flows in one direction)

• Transpirations occurs more rapidly in light, high temps, dry air (osmosis: air is low water concentration, leaf is high)

Capillary Action:

• Water rises up the walls of the xylem tube as a result of the forces of cohesion, adhesion, and surface tension

• The thinner the tube, the more the water will want to attach to it

Root Pressure:

• So much water in the soil that the push from the soil causes water from the leaf tips to produce water droplets

What is Stomata (stoma)?

• Pores in the epidermis of leaves

• Purpose is to allow CO2 into the leaf for photosynthesis and oxygen out

  • Allows the exchange of gasses

• This causes water to evaporate out of the stomata

• Can open and close to regulate the amount of water in the leaf

How do plants regulate water loss?

• Surface is covered in stomata

• Each stomata is surrounded by guard cells

  • If the plant doesn’t have enough water, it becomes flaccid and the guard cells close

  • If the plant has lots of water, it becomes turgid and the guard cells open up to allow the release of water

    • The cell will then lose water, decreasing the turgidness in the guard cells, causing the stomata to close